Organic light emitting diode display

ABSTRACT

An OLED display device includes a pixel having a switching transistor turned on by a scan signal received from a scan line and which transmits a data signal received from a data line to a first node, a driving transistor connected between the first node and a second node and through which a driving current corresponding to the data signal flows, a storage capacitor including one end connected to a power supply and another end connected to a gate electrode of the driving transistor, an OLED emitting light by the driving current, and a light emission control transistor connected between the second node and an anode of the OLED and which is turned on by an light emission control signal and transmits the driving current to the OLED. The switching transistor may be an n-type transistor, and the light emission control transistor is a p-type transistor.

This application claims priority to Korean Patent Application No.10-2016-0153902, filed on Nov. 18, 2016, and all the benefits accruingtherefrom under 35 U.S.C. § 119, the content of which in its entirety isherein incorporated by reference.

BACKGROUND (a) Field

Exemplary embodiments of the invention relate to an organic lightemitting diode display device.

(b) Description of the Related Art

An organic light emitting diode display device uses an organic lightemitting diode (“OLED”) of which luminance is controlled by a current ora voltage. In general, the organic light emitting diode display deviceis classified into a passive matrix OLED (“PMOLED”) and an active matrixOLED (“AMOLED”) according to a driving mode of the OLED. Among theOLEDs, the AMOLED, which emits light selected for each unit pixel interms of resolution, contrast, and operation speed, has become popular.

A pixel of the AMOLED includes an organic light emitting diode and acircuit portion for supplying a current to the organic light emittingdiode.

Transistors included in the conventional circuit portion are thosehaving a low-temperature polycrystalline silicon (“LTPS”) semiconductorlayer. The LTPS transistor consumes a high amount of power due to a highturn-off current. That is, the LTPS transistor is turned off by a largeamount of current.

A transistor including an oxide semiconductor having a low turn-offcurrent has been researched to be used as a semiconductor layer so thatthe transistor included in the circuit portion may operate at low power.

SUMMARY

Exemplary embodiments of the invention are directed to an organic lightemitting diode display device that may operate at low power.

In addition, Exemplary embodiments of the invention are directed to anorganic light emitting diode display device that may prevent luminanceof a black image from increasing.

According to an exemplary embodiment of the invention, an organic lightemitting diode display device includes a plurality of pixels, aplurality of scan lines connected to the plurality of pixels and whichtransmits corresponding scan signals to the plurality of pixels, aplurality of initialization lines connected to the plurality of pixelsand which transmits corresponding initialization signals to theplurality of pixels, a plurality of light emission control linesconnected to the plurality of pixels and which transmits correspondinglight emission control signals to the plurality of pixels, and aplurality of data lines connected to the plurality of pixels and whichtransmits corresponding data signals to the plurality of pixels, whereat least one of the plurality of pixels includes a switching transistorturned on by a scan signal received from a corresponding one of theplurality of scan lines and which transmits a data signal received froma corresponding one of the plurality of data lines to a first node, adriving transistor connected between the first node and a second nodeand through which a driving current corresponding to the data signalflows, a storage capacitor which includes a first end connected to apower supply and a second end connected to a gate electrode of thedriving transistor, an organic light emitting diode which emits lightbased on the driving current, the driving current flows through theorganic light emitting diode, and a light emission control transistorconnected between the second node and an anode of the organic lightemitting diode and which is turned on by an light emission controlsignal received from a corresponding one of the plurality of lightemission control lines and which transmits the driving current to theorganic light emitting diode, and the switching transistor may be ann-type transistor, and the light emission control transistor is a p-typetransistor.

In an exemplary embodiment, the light emission control transistor may bea low-temperature polycrystalline silicon (“LTPS”) semiconductortransistor, and the switching transistor may be an oxide semiconductortransistor.

In an exemplary embodiment, the organic light emitting diode displaydevice may further include a compensation transistor which compensates athreshold voltage of the driving transistor and is connected to thedriving transistor.

In an exemplary embodiment, the organic light emitting diode displaydevice may further include an initialization transistor turned on by aninitialization signal received from a corresponding one of the pluralityof initialization lines and which applies an initialization voltage tothe gate electrode of the driving transistor.

In an exemplary embodiment, the organic light emitting diode displaydevice may further include a reset transistor turned on by the scansignal and which applies the initialization voltage to the anode of theorganic light emitting diode.

In an exemplary embodiment, the compensation transistor, theinitialization transistor, and the reset transistor may be n-typetransistors.

In an exemplary embodiment, the compensation transistor, theinitialization transistor, and the reset transistor may be oxidesemiconductor transistors.

In an exemplary embodiment, the organic light emitting diode displaydevice may further include an operation control transistor turned on bythe light emission control signal and which connects the first node andthe power supply.

In an exemplary embodiment, the operation control transistor may be ap-type transistor.

In an exemplary embodiment, the operation control transistor may be ann-type transistor.

According to another exemplary embodiment of the invention, an organiclight emitting diode display device includes a plurality of pixels, aplurality of scan lines connected to the plurality of pixels and whichtransmits corresponding scan signals to the plurality of pixels, aplurality of initialization lines connected to the plurality of pixelsand which transmits corresponding initialization signals to theplurality of pixels, a plurality of light emission control linesconnected to the plurality of pixels and which transmits correspondinglight emission control signals to the plurality of pixels, and aplurality of data lines connected to the plurality of pixels and whichtransmits corresponding data signals to the plurality of pixels, whereat least one of the plurality of pixels includes a switching transistorturned on by a scan signal received from a corresponding one of theplurality of scan lines and which transmits a data signal received froma corresponding one of the plurality of data lines to a first node, adriving transistor connected between the first node and a second nodeand through which a driving current corresponding to the data signalflows, a storage capacitor which includes a first end connected to apower supply and a second end connected to a gate electrode of thedriving transistor, an organic light emitting diode which emits light bythe driving current, where the driving current flows through the organiclight emitting diode, and a light emission control transistor connectedbetween the second node and an anode of the organic light emitting diodeand which is turned on by an light emission control signal received froma corresponding one of the plurality of light emission control lines andwhich transmits the driving current to the organic light emitting diode,and the at least one of the plurality of pixels may include both ann-type transistor provided with an oxide semiconductor layer and ap-type transistor provided with an LTPS semiconductor layer.

In an exemplary embodiment, the switching transistor may be the n-typetransistor provided with the oxide semiconductor layer, and the drivingtransistor and the light emission control transistor may be the p-typetransistors provided with the LTPS semiconductor layer.

In an exemplary embodiment, the organic light emitting diode displaydevice may further include a compensation transistor which compensates athreshold voltage of the driving transistor and is connected to thedriving transistor, an initialization transistor turned on by aninitialization signal received from a corresponding one of the pluralityof initialization lines and which applies an initialization voltage tothe gate electrode of the driving transistor, and a reset transistorturned on by the scan signal and which applies the initializationvoltage to the anode of the organic light emitting diode.

In an exemplary embodiment, the compensation transistor, theinitialization transistor, and the reset transistor may be the n-typetransistors provided with the oxide semiconductor layer.

In an exemplary embodiment, the organic light emitting diode displaydevice may further include an operation control transistor turned on bythe light emission control and which connects the first node and thepower supply.

In an exemplary embodiment, the operation control transistor may be thep-type transistor provided with the LTPS semiconductor layer.

In an exemplary embodiment, the operation control transistor may be then-type transistor provided with the oxide semiconductor layer.

According to exemplary embodiments of the invention, it is possible toreduce power consumption of an organic light emitting diode displaydevices.

According to exemplary embodiments of the invention, it is possible toimprove display quality of an organic light emitting diode displaydevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an exemplary embodiment of anorganic light emitting diode display device.

FIG. 2 illustrates a circuit diagram of an exemplary embodiment of apixel of an organic light emitting diode display device.

FIG. 3 illustrates a timing chart of an exemplary embodiment of adriving method of an organic light emitting diode display device in oneframe.

FIG. 4 illustrates a block diagram of another exemplary embodiment of anorganic light emitting diode display device.

FIG. 5 illustrates a circuit diagram of another exemplary embodiment ofa pixel of an organic light emitting diode display device.

FIG. 6 illustrates a timing chart of another exemplary embodiment of adriving method of an organic light emitting diode display device in oneframe.

DETAILED DESCRIPTION

The invention will be described more fully hereinafter with reference tothe accompanying drawings, in which exemplary embodiments are shown. Asthose skilled in the art would realize, the described embodiments may bemodified in various different ways, all without departing from thespirit or scope of the present invention.

To clearly describe exemplary embodiments of the invention, portionswhich do not relate to the description are omitted, and like referencenumerals designate like elements throughout the specification.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “At least one” is not to be construed as limiting “a” or“an.”

In addition, unless explicitly described to the contrary, the word“comprise” and variations such as “comprises” or “comprising” will beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Hereinafter, an organic light emitting diode display device 10 accordingto an exemplary embodiment will be described with reference to FIG. 1.

FIG. 1 illustrates a schematic block diagram of an exemplary embodimentof an organic light emitting diode display device according to theinvention.

The organic light emitting diode display device 10 may include a displaypanel 100, a data driver 110, a scan driver 120, an initializationdriver 130, a light emission driver 140, a power supply 150, and asignal controller 160. The elements shown in FIG. 1 are not essential tothe exemplary embodiment of the organic light emitting diode displaydevice. Thus, the organic light emitting diode display device describedin the present specification may include a larger or smaller number ofelements than those described above.

The display panel 100 includes a plurality of display signal lines and aplurality of pixels P connected to the plurality of display signallines. The plurality of display signal lines include a plurality of scanlines GW1 to GWm for transmitting a plurality of scan signals, which arealso referred to as gate signals, a plurality of initialization linesGI1 to GIm for transmitting a plurality of initialization signals, aplurality of light emission control lines EM1 to EMm for transmitting aplurality of light emission control signals, and a plurality of datalines D1 to Dn for transmitting a plurality of data voltages. Theplurality of pixels P may be connected to the corresponding scan linesGW1 to GWm, the corresponding initialization lines GI1 to GIm, thecorresponding light emission control lines EM1 to EMm, and thecorresponding data lines D1 to Dn, respectively. Each of the pluralityof pixels P may include an organic light emitting element. Each of theplurality of pixels P displays an image depending on a data voltagetransmitted thereto.

Each of the plurality of pixels P of the display panel 100 receives aninitialization voltage VINT, a first power voltage ELVDD, and a secondpower voltage ELVSS from the power supply 150.

The data driver 110 is connected to the plurality of data lines D1 to Dnof the display panel 100, and applies the plurality of data voltages tothe plurality of data lines D1 to Dn. Specifically, a data driver IC maygenerate data voltages for all gray levels using reference gammavoltages. The data driver 110 outputs the generated data voltages asdata signals to the data lines D1 to Dn.

A control signal CONT1 is an operation control signal of the data driver110, that is generated and transmitted by the signal controller 160.

The scan driver 120 is connected to the display panel 100 through theplurality of scan lines GW1 to GWm. The scan driver 120 generates theplurality of scan signals according to a control signal CONT2 andrespectively transmits the generated scan signals to corresponding scanlines.

The initialization driver 130 is connected to the display panel 100through the plurality of initialization lines GI1 to GIm. Theinitialization driver 130 generates the plurality of initializationsignals according to a control signal CONT3 and respectively transmitsthem to corresponding initialization lines.

The control signals CONT2 and CONT3 are operation control signals of thescan driver 120 and the initialization driver 130, respectively, thatare generated and transmitted by the signal controller 160. The controlsignals CONT2 and CONT3 may include different clock signals from each ofscan start signals of the scan driver 120 and the initialization driver130.

The light emission driver 140 generates the plurality of light emissioncontrol signals according to the light emission control signal CONT4.The light emission driver 140 transmits the plurality of light emissioncontrol signals to the plurality of light emission control lines EM1 toEMm, respectively.

The power supply 150 may supply the initialization voltage VINT forinitializing a gate electrode of a driving transistor and an anode N1 ofan organic light emitting diode included in each pixel P of the displaypanel 100 to a predetermined voltage and supply the first and secondpower voltages ELVDD and ELVSS for driving each pixel P.

The signal controller 160 receives an input image signal IS and an inputcontrol signal CTRL from the outside. The input image signal IS includesluminance information of each pixel of the display panel 100, and theluminance may be quantized into gray levels of a predetermined number,for example, 1024, 256, or 64.

The input control signal CTRL may include a vertical synchronizationsignal, a horizontal synchronization signal, a main clock signal, a dataenable signal, etc. associated with the image provided by the inputimage signal IS.

The signal controller 160 generates control signals CONT1 to CONT5 andan image data signal DATA according to the input image signal IS and theinput control signal CTRL.

Specifically, the signal controller 160 processes the image signal ISaccording to operating conditions of the display panel 100 and the datadriver 110 based on the input image signal IS and the input controlsignal CTRL. In an exemplary embodiment, for example, the signalcontroller 160 may generate the image data signal DATA through imageprocessing processes such as gamma correction and luminance compensationon the image signal IS.

The signal controller 160 generates the control signal CONT1 forcontrolling the operation of the data driver 110, and transmits it tothe data driver 110 together with the image-processed data signal DATA.In addition, the signal controller 160 transmits the control signalCONT2 for controlling the operation of the scan driver 120 to the scandriver 120. Further, the signal controller 160 transmits the controlsignal CONT3 for controlling the operation of the initialization driver130 to the initialization driver 130. Moreover, the signal controller160 may transmit the light emission control signal CONT4 to the lightemission driver 140 to drive the light emission driver 140.

The signal controller 160 may control an operation of the power supply150. In an exemplary embodiment, for example, the signal controller 160may transmit a power control signal CONT5 to the power supply 150 todrive the power supply 150. The power supply 150 is connected to a powerline (not shown) provided in the display panel 100.

An exemplary embodiment of a pixel P of the organic light emitting diodedisplay device 10 according to the invention will now be described indetail with reference to FIG. 2.

FIG. 2 illustrates a circuit diagram of an exemplary embodiment of apixel of an organic light emitting diode display device according to theinvention. As shown in FIG. 2, an exemplary embodiment of one pixel ofthe organic light emitting diode display device 10 according to theinvention may include a plurality of transistors T1 to T7, a storagecapacitor Cst, and an organic light emitting diode OLED.

The plurality of transistors may include a driving transistor T1, aswitching transistor T2, a compensation transistor T3, an initializationtransistor T4, an operation control transistor T5, a light emissioncontrol transistor T6, and a reset transistor T7.

The signal lines connected to each pixel may include a scan line fortransmitting a scan signal GW[i], an initialization line fortransmitting an initialization signal GI[i] to the initializationtransistor T4, a light emission control line for transmitting a lightemission control signal EM[i] to the operation control transistor T5 andthe light emission control transistor T6, a data line for transmitting adata signal D[j], a power line for transmitting the first power voltageELVDD, and an initialization voltage line for transmitting theinitialization voltage VINT that initializes the driving transistor T1and the organic light emitting diode OLED.

In a pixel connected to i-th row signal lines and j-th column signalline, a gate electrode of the driving transistor T1 is connected to afirst end of the storage capacitor Cst, a first electrode of the drivingtransistor T1 is connected to the power line for transmitting the firstpower voltage ELVDD via the operation control transistor T5, and asecond electrode of the driving transistor T1 is electrically connectedto an anode N1 of the organic light emitting diode OLED via the lightemission control transistor T6. The first and second electrodes of thedriving transistor T1 are different electrodes from the gate electrodeof the driving transistor T1. The driving transistor T1 receives thedata signal D[j] according to a switching operation of the switchingtransistor T2 and then supplies a driving current to the organic lightemitting diode OLED via the light emission control transistor T6.

A gate electrode of the switching transistor T2 is connected to the scanline for transmitting the scan signal GW[i], a first electrode of theswitching transistor T2 is connected to the data line for transmittingthe data signal D[j], and a second electrode of the switching transistorT2 is connected to the power line for transmitting the first powervoltage ELVDD via the operation control transistor T5 and connected tothe first electrode of the driving transistor T1. The first and secondelectrodes of the switching transistor T2 are different electrodes fromthe gate electrode of the switching transistor T2.

The switching transistor T2 is turned on according to the scan signalGW[i]transmitted through the scan line and then transmits the datasignal D[j] transmitted from the data line to the first electrode of thedriving transistor T1, through the switching operation thereof.

A gate electrode of the compensation transistor T3 is connected to thescan line, a first electrode of the compensation transistor T3 isconnected to the anode N1 of the organic light emitting diode OLED viathe light emission control transistor T6 and connected to the secondelectrode of the driving transistor T1, and a second electrode of thecompensation transistor T3 is connected to the first end of the storagecapacitor Cst, a first electrode of the initialization transistor T4,and the gate electrode of the driving transistor T1. The first andsecond electrodes of the compensation transistor T3 are differentelectrodes from the gate electrode of the compensation transistor T3.

The compensation transistor T3 is turned on according to the scan signalGW[i]transmitted through the scan line and then connects the gateelectrode and the second electrode of the driving transistor T1 to eachother, such that the driving transistor T1 may be operated as a diode.

A gate electrode of the initialization transistor T4 is connected to theinitialization line for transmitting the initialization signal GI[i], asecond electrode of the initialization transistor T4 is connected to theinitialization voltage line for transmitting the initialization voltageVINT, and the first electrode of the initialization transistor T4 isconnected to the first end of the storage capacitor Cst, the secondelectrode of the compensation transistor T3, and the gate electrode ofthe driving transistor T1. The first and second electrodes of theinitialization transistor T4 are different electrodes from the gateelectrode of the initialization transistor T4.

The initialization transistor T4 is turned on according to theinitialization signal GI[i] transmitted through the initialization linefor transmitting the initialization signal GI[i] and then transmits theinitialization voltage VINT to the gate electrode of the drivingtransistor T1 such that a voltage of the gate electrode of the drivingtransistor T1 may be initialized.

A gate electrode of the operation control transistor T5 is connected tothe light emission control line for transmitting the light emissioncontrol signal EM[i], a first electrode of the operation controltransistor T5 is connected to the power line for transmitting the firstpower voltage ELVDD, and a second electrode of the operation controltransistor T5 is connected to the first electrode of the drivingtransistor T1 and the second electrode of the switching transistor T2.The first and second electrodes of the operation control transistor T5are different electrodes from the gate electrode of the operationcontrol transistor T5.

A gate electrode of the light emission control transistor T6 isconnected to the light emission control line, a first electrode of thelight emission control transistor T6 is connected to the secondelectrode of the driving transistor T1 and the first electrode of thecompensation transistor T3, and a second electrode of the light emissioncontrol transistor T6 is electrically connected to the anode N1 of theorganic light emitting diode OLED and a first electrode of the resettransistor T7. The first and second electrodes of the light emissioncontrol transistor T6 are different electrodes from the gate electrodeof the light emission control transistor T6.

The operation control transistor T5 and the light emission controltransistor T6 are simultaneously turned on depending on the lightemission control signal EM[i]transmitted through the light emissioncontrol line, and in this case, the first power voltage ELVDD istransmitted to the organic light emitting diode OLED such that a drivingcurrent flows through the organic light emitting diode OLED.

A gate electrode of the reset transistor T7 is connected to the scanline, a second electrode of the reset transistor T7 is connected to theinitialization voltage line for transmitting the initialization voltageVINT and the second electrode of the initialization transistor T4, andthe first electrode of the reset transistor T7 is electrically connectedto the anode N1 of the organic light emitting diode OLED and the secondelectrode of the light emission control transistor T6. The first andsecond electrodes of the reset transistor T7 are different electrodesfrom the gate electrode of the reset transistor T7.

The reset transistor T7 is simultaneously turned on with the switchingtransistor T2 according to the scan signal GW[i] transmitted through thescan line and then initializes a voltage of the anode N1 of the organiclight emitting diode OLED with the initialization voltage VINT.

The second end of the storage capacitor Cst is connected to the powerline for transmitting the first power voltage ELVDD, and a cathode ofthe organic light emitting diode OLED is connected to the power voltageELVSS. Accordingly, the organic light emitting diode OLED receives thedriving current from the driving transistor T1 to emit light, thus theorganic light emitting diode display device 10 displays an image.

One pixel P of the display panel 100 includes at least two differenttypes of transistors.

The driving transistor T1, the operation control transistor T5, and thelight emission control transistor T6 among the transistors T1 to T7included in one pixel P may be p-type transistors. A gate-on voltage forturning on the p-type transistor is a low-level voltage, and a gate-offvoltage for turning it off is a high-level voltage.

The switching transistor T2, the compensation transistor T3, theinitialization transistor T4, and the reset transistor T7 among thetransistors T1 to T7 may be n-type transistors. A gate-on voltage forturning on the n-type transistor is a high-level voltage, and a gate-offvoltage for turning it off is a low-level voltage.

The driving transistor T1, the operation control transistor T5, and thelight emission control transistor T6 may be LTPS transistors (“LTPSTFTs”) having a polysilicon semiconductor layer. The switchingtransistor T2, the compensation transistor T3, the initializationtransistor T4, and the reset transistor T7 may be oxide semiconductors(“oxide TFTs”) having an oxide semiconductor layer. In exemplaryembodiments, the oxide semiconductor layer of the oxide transistor maybe made of various metal oxides.

In an exemplary embodiment, the oxide semiconductor layer may include anoxide based on titanium (Ti), hafnium (Hf), zirconium (Zr), aluminum(Al), tantalum (Ta), germanium (Ge), zinc (Zn), gallium (Ga), tin (Sn),or indium (In), and complex oxides thereof such as zinc oxide (ZnO),indium-gallium-zinc oxide (In—Ga—Zn—O), indium-zinc oxide (In—Zn—O),zinc-tin oxide (Zn—Sn—O) indium-gallium oxide (In—Ga—O), indium-tinoxide (In—Sn—O), indium-zirconium oxide (In—Zr—O), indium-zirconium-zincoxide (In—Zr—Zn—O), indium-zirconium-tin oxide (In—Zr—Sn—O),indium-zirconium-gallium oxide (In—Zr—Ga—O), indium-aluminum oxide(In—Al—O), indium-zinc-aluminum oxide (In—Zn—Al—O), indium-tin-aluminumoxide (In—Sn—Al—O), indium-aluminum-gallium oxide (In—Al—Ga—O),indium-tantalum oxide (In—Ta—O), indium-tantalum-zinc oxide(In—Ta—Zn—O), indium-tantalum-tin oxide (In—Ta—Sn—O),indium-tantalum-gallium oxide (In—Ta—Ga—O), indium-germanium oxide(In—Ge—O), indium-germanium-zinc oxide (In—Ge—Zn—O),indium-germanium-tin oxide (In—Ge—Sn—O), indium-germanium-gallium oxide(In—Ge—Ga—O), titanium-indium-zinc oxide (Ti—In—Zn—O), andhafnium-indium-zinc oxide (Hf—In—Zn—O).

A driving method of the organic light emitting diode display device 10including the pixel P shown in FIG. 2 will now be described withreference to FIG. 3.

FIG. 3 illustrates a timing chart of an exemplary embodiment of adriving method of an organic light emitting diode display device in oneframe according to the invention.

At a first time t1 within a period (1 Frame) which is a duration that animage of one frame is displayed, the initialization signal GI[i] appliedto an i-th row initialization line is changed from a low level voltageto a high level voltage.

The initialization transistor T4 is turned on by the high level voltageof the initialization signal GI[i]. From the first time t1 to a secondtime t2 at which the high level voltage of the initialization signalGI[i] is changed to the low level voltage, the gate electrode of thedriving transistor T1 is initialized with the initialization voltageVINT transmitted through the turned-on initialization transistor T4.

At the second time t2, the scan signal GW[i] applied to an i-th scanline is changed from the low level voltage to the high level voltage. Inaddition, the data signal D[j] is applied to a j-th column data line.

The switching transistor T2, the compensation transistor T3, and thereset transistor T7 are turned on by the high level voltage of the scansignal GW[i]. From the second time t2 to a third time t3 at which thescan signal GW[i] is changed from the high level voltage to the lowlevel voltage, a voltage which amounts to a compensated voltage of thedata signal D[j] by a threshold voltage of the driving transistor T1through the turned-on switching transistor T2 and the turned-oncompensation transistor T3 is applied to the gate electrode of thedriving transistor T1 and is stored in the storage capacitor Cst. Thecompensation transistor T3 compensates the threshold voltage of thedriving transistor T1.

In addition, from the second time t2 to a third time t3, a voltage V_N1of the anode N1 of the organic light emitting diode OLED is changed froma remaining voltage VPRE which was a voltage of the anode N1 during aprevious frame period to the initialization voltage VINT transmittedthrough the turned-on reset transistor T7.

Then, at a fourth time t4, the light emission control signal EM[i]applied to an i-th row light emission control line is changed from ahigh level voltage to a low level voltage.

The operation control transistor T5 and the light emission controltransistor T6 are turned on by the low level voltage of the lightemission control signal EM[i]. Thus, a driving current corresponding toa voltage difference between the voltage of the gate electrode of thedriving transistor T1 and the first power voltage ELVDD is supplied tothe organic light emitting diode OLED through the light emission controltransistor T6.

When the reset transistor T7 is turned off at the third time t3, theanode N1 of the organic light emitting diode OLED becomes in a floatingstate. Accordingly, the light emission control signal EM[i] applied tothe light emission control transistor T6 may affect the voltage V_N1 ofthe anode N1.

It is assumed that a black data signal of gray level 0 which representsa black image is applied to the pixel P. In this case, if the lightemission control transistor T6 is an n-type transistor, the high levelvoltage of the emission control signal EM[i] should be applied to thegate electrode of the light emission control transistor T6 in order toturn on the light emission control transistor T6. When the high levelvoltage of light emission control signal EM[i] is applied to the gateelectrode of the light emission control transistor T6, the voltage V_N1of the anode N1 in the floating state increases. A current may flowthrough the organic light emitting diode OLED due to the increasedvoltage V_N1 of the anode N1. Therefore, if the light emission controltransistor T6 is the n-type transistor, the black image may not beaccurately displayed due to the current flowing through the organiclight emitting diode OLED.

However, in the organic light emitting diode display device 10 accordingto the invention, since the light emission control transistor T6 is thep-type transistor, the low level voltage of the light emission controlsignal EM[i] applied to the gate electrode of the light emission controltransistor T6 can turn on the light emission control transistor T6. Inthe case of displaying the black image, since the low level voltage ofthe light emission control signal EM[i] is applied to the gate electrodeof the light emission control transistor T6, the voltage V_N1 of theanode N1 in the floating state decreases. Since the current is preventedfrom flowing through the organic light emitting diode OLED due to thedecreased voltage V_N1 of the anode N1, the organic light emitting diodedisplay device 10 according to the invention may accurately display theblack image.

Hereinafter, another exemplary embodiment of an organic light emittingdiode display device according to the invention will be described withreference to FIG. 4 to FIG. 6.

FIG. 4 illustrates a block diagram of another exemplary embodiment of anorganic light emitting diode display device according to the invention.Among elements shown in FIG. 4, a detailed description for the sameelements as those shown in FIG. 1 will be omitted. An organic lightemitting diode display device 10′ includes the display panel 100, thedata driver 110, the scan driver 120, the initialization driver 130, afirst light emission driver 142, a second light emission driver 144, thepower supply 150, and the signal controller 160.

The display panel 100 includes a plurality of display signal lines and aplurality of pixels P′ connected to the plurality of display signallines. The plurality of display signal lines include a plurality of scanlines GW1 to GWm for transmitting a plurality of scan signals, which arealso referred to as gate signals, a plurality of initialization linesGI1 to GIm for transmitting a plurality of initialization signals, afirst plurality of light emission control lines EMa1 to EMam fortransmitting a plurality of first light emission control signals, asecond plurality of light emission control lines EMb1 to EMbm fortransmitting a plurality of second light emission control signals, and aplurality of data lines D1 to Dn for transmitting a plurality of datavoltages.

The first light emission driver 142 generates the plurality of firstlight emission control signals depending on a light emission controlsignal CONT41. The first light emission driver 142 transmits theplurality of first light emission control signals to the first lightemission control lines EMa1 to EMam, respectively.

The second light emission driver 144 generates the plurality of secondlight emission control signals depending on a light emission controlsignal CONT42. The second light emission driver 144 transmits theplurality of second light emission control signals to the second lightemission control lines EMb1 to EMbm, respectively.

An exemplary embodiment of a pixel P′ of the organic light emittingdiode display device 10′ according to the invention will now bedescribed in detail with reference to FIG. 5.

FIG. 5 illustrates a circuit diagram of another exemplary embodiment ofa pixel of an organic light emitting diode display device according tothe invention. As shown in FIG. 5, an exemplary embodiment of one pixelof the organic light emitting diode display device 10′ according to theinvention includes a plurality of transistors T1 to T7, a storagecapacitor Cst, and an organic light emitting diode OLED. Among elementsshown in FIG. 5, a detailed description for the same elements as thoseshown in FIG. 2 will be omitted.

The signal lines connected to each pixel may include a scan line fortransmitting a scan signal GW[i], an initialization line fortransmitting an initialization signal GI[i] to the initializationtransistor T4, a first light emission control line for transmitting afirst light emission control signal EMa[i] to the operation controltransistor T5, a second light emission control line for transmitting asecond light emission control signal EMb[i] to the light emissioncontrol transistor T6, a data line for transmitting a data signal D[j],a power line for transmitting the first power voltage ELVDD, and aninitialization voltage line for transmitting the initialization voltageVINT that initializes the driving transistor T1 and the organic lightemitting diode OLED.

The gate electrode of the operation control transistor T5 is connectedto the first light emission control line for transmitting the firstlight emission control signal EMa[i], the first electrode of theoperation control transistor T5 is connected to the power line, and thesecond electrode of the operation control transistor T5 is connected tothe first electrode of the driving transistor T1 and the secondelectrode of the switching transistor T2.

The gate electrode of the light emission control transistor T6 isconnected to the second light emission control line for transmitting thesecond light emission control signal EMb[i], the first electrode of thelight emission control transistor T6 is connected to the secondelectrode of the driving transistor T1 and the first electrode of thecompensation transistor T3, and the second electrode of the lightemission control transistor T6 is connected to the anode N1 of theorganic light emitting diode OLED and the first electrode of the resettransistor T7.

The operation control transistor T5 and the light emission controltransistor T6 are simultaneously turned on depending on the first lightemission control signal EMa[i] transmitted through the first lightemission control line and the second light emission control signalEMb[i] transmitted through the second light emission control line, andin this case, the first power voltage ELVDD is transmitted to theorganic light emitting diode OLED such that a driving current flowsthrough the organic light emitting diode OLED.

The driving transistor T1 and the light emission control transistor T6among the transistors T1 to T7 included in one pixel P′ may be p-typetransistors.

The switching transistor T2, the compensation transistor T3, theinitialization transistor T4, the operation control transistor T5, andthe reset transistor T7 among the transistors T1 to T7 may be n-typetransistors.

In addition, the driving transistor T1 and the light emission controltransistor T6 may be LTPS transistors (“LTPS TFTs”) having a polysiliconsemiconductor layer.

The switching transistor T2, the compensation transistor T3, theinitialization transistor T4, the operation control transistor T5, andthe reset transistor T7 may be oxide semiconductors (“oxide TFTs”)having an oxide semiconductor layer.

A driving method of the organic light emitting diode display device 10′including the pixel P′ shown in FIG. 5 will be described with referenceto FIG. 6.

FIG. 6 illustrates a timing chart of another exemplary embodiment of adriving method of an organic light emitting diode display device in oneframe according to the invention.

At a first time t1 within a period (1 Frame) which is a duration that animage of one frame is displayed, the initialization signal GI[i] appliedto an i-th row initialization line is changed from a low level voltageto a high level voltage.

The initialization transistor T4 is turned on by the high level voltageof the initialization signal GI[i]. From the first time t1 to a secondtime t2 at which the high level voltage of the initialization signalGI[i] is changed to the low level voltage, the gate electrode of thedriving transistor T1 is initialized with the initialization voltageVINT transmitted through the turned-on initialization transistor T4.

At the second time t2, the scan signal GW[i] applied to an i-th scanline is changed from the low level voltage to the high level voltage. Inaddition, the data signal D[j] is applied to a j-th column data line.

The switching transistor T2, the compensation transistor T3, and thereset transistor T7 are turned on by the high level voltage of the scansignal GW[i]. From the second time t2 to a third time t3 at which thescan signal GW[i] is changed from the high level voltage to the lowlevel voltage, a voltage which amounts to a compensated voltage of thedata signal D[j] by a threshold voltage of the driving transistor T1through the turned-on switching transistor T2 and the turned-oncompensation transistor T3 is applied to the gate electrode of thedriving transistor T1 and is stored in the storage capacitor Cst.

In addition, from the second time t2 to a third time t3, a voltage V_N1of the anode N1 of the organic light emitting diode OLED is changed froma remaining voltage VPRE which was a voltage of the anode N1 during aprevious frame period to the initialization voltage VINT transmittedthrough the turned-on reset transistor T7.

Then, at a fourth time t4, the first light emission control signalEMa[i] applied to an i-th row first light emission control line ischanged from a low level voltage to a high level voltage, and the secondlight emission control signal EMb[i] applied to an i-th row second lightemission control line is changed from the high level voltage to the lowlevel voltage.

The operation control transistor T5 is turned on by the high levelvoltage of the first light emission control signal EMa[i].

In addition, the light emission control transistor T6 is turned on bythe low level voltage of the second light emission control signalEMb[i]. Thus, a driving current corresponding to a voltage differencebetween the voltage of the gate electrode of the driving transistor T1and the first power voltage ELVDD is supplied to the organic lightemitting diode OLED through the light emission control transistor T6.

When the reset transistor T7 is turned off at the third time t3, theanode N1 of the organic light emitting diode OLED becomes in a floatingstate. Accordingly, the light emission control signal EM[i] applied tothe light emission control transistor T6 may affect the voltage V_N1 ofthe anode N1.

It is assumed that a black data signal of gray level 0 which representsa black image is applied to the pixel P′. In this case, if the lightemission control transistor T6 is an n-type transistor, the high levelvoltage of the emission control signal EM[i] should be applied to thegate electrode of the light emission control transistor T6 in order toturn on the light emission control transistor T6. When the high levelvoltage of the light emission control signal EM[i] is applied to thegate electrode of the light emission control transistor T6, the voltageV_N1 of the anode N1 in the floating state increases. A current may flowthrough the organic light emitting diode OLED due to the increasedvoltage V_N1 of the anode N1. Therefore, if the light emission controltransistor T6 is the n-type transistor, the black image may not beaccurately displayed due to the current flowing through the organiclight emitting diode OLED.

However, in the organic light emitting diode display device 10′according to the invention, since the light emission control transistorT6 is the p-type transistor, the low level voltage of the light emissioncontrol signal EM[i] applied to the gate electrode of the light emissioncontrol transistor T6 can turn on the light emission control transistorT6. In the case of displaying the black image, since the low levelvoltage of the light emission control signal EM[i] is applied to thegate electrode of the light emission control transistor T6, the voltageV_N1 of the anode N1 of the floating state decreases. Since the currentis prevented from flowing through the organic light emitting diode OLEDdue to the decreased voltage V_N1 of the anode N1, the organic lightemitting diode display device 10′ according to invention may accuratelydisplay the black image. In addition, since the operation controltransistor T5 is an oxide semiconductor transistor having a low turn-offcurrent, it is possible to reduce power consumption of an organic lightemitting diode display device.

While the invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosed exemplaryembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. An organic light emitting diode display devicecomprising: a plurality of pixels; a plurality of scan lines connectedto the plurality of pixels and which transmits corresponding scansignals to the plurality of pixels; a plurality of initialization linesconnected to the plurality of pixels and which transmits correspondinginitialization signals to the plurality of pixels; a plurality of lightemission control lines connected to the plurality of pixels and whichtransmits corresponding light emission control signals to the pluralityof pixels; and a plurality of data lines connected to the plurality ofpixels and which transmits corresponding data signals to the pluralityof pixels, wherein at least one of the plurality of pixels includes aswitching transistor turned on by a scan signal received from acorresponding one of the plurality of scan lines and which transmits adata signal received from a corresponding one of the plurality of datalines to a first node, a driving transistor connected between the firstnode and a second node and through which a driving current correspondingto the data signal flows, a storage capacitor which includes a first endconnected to a power supply and a second end connected to a gateelectrode of the driving transistor, an organic light emitting diodewhich emits light based on the driving current, wherein the drivingcurrent flows through the organic light emitting diode, a light emissioncontrol transistor connected between the second node and an anode of theorganic light emitting diode and which is turned on by an light emissioncontrol signal received from a corresponding one of the plurality oflight emission control lines and which transmits the driving current tothe organic light emitting diode, an initialization transistor turned onby an initialization signal received from a corresponding one of theplurality of initialization lines and which applies an initializationvoltage to the gate electrode of the driving transistor; and a resettransistor turned on by the scan signal and which applies theinitialization voltage directly to the anode of the organic lightemitting diode, wherein the switching transistor is an n-typetransistor, and the light emission control transistor is a p-typetransistor.
 2. The organic light emitting diode display device of claim1, wherein the light emission control transistor is a low-temperaturepolycrystalline silicon (LTPS) semiconductor transistor, and theswitching transistor is an oxide semiconductor transistor.
 3. Theorganic light emitting diode display device of claim 2, furthercomprising a compensation transistor which compensates a thresholdvoltage of the driving transistor and is connected to the drivingtransistor.
 4. The organic light emitting diode display device of claim1, wherein the compensation transistor, the initialization transistor,and the reset transistor are n-type transistors.
 5. The organic lightemitting diode display device of claim 4, wherein the compensationtransistor, the initialization transistor, and the reset transistor areoxide semiconductor transistors.
 6. The organic light emitting diodedisplay device of claim 1, further comprising an operation controltransistor turned on by the light emission control signal and whichconnects the first node and the power supply.
 7. The organic lightemitting diode display device of claim 6, wherein the operation controltransistor is a p-type transistor.
 8. The organic light emitting diodedisplay device of claim 6, wherein the operation control transistor isan n-type transistor.
 9. An organic light emitting diode display devicecomprising: a plurality of pixels; a plurality of scan lines connectedto the plurality of pixels and which transmits corresponding scansignals to the plurality of pixels; a plurality of initialization linesconnected to the plurality of pixels and which transmits correspondinginitialization signals to the plurality of pixels; a plurality of lightemission control lines connected to the plurality of pixels and whichtransmits corresponding light emission control signals to the pluralityof pixels; and a plurality of data lines connected to the plurality ofpixels and which transmits corresponding data signals to the pluralityof pixels, wherein at least one of the plurality of pixels includes aswitching transistor turned on by a scan signal received from acorresponding one of the plurality of scan lines and which transmits adata signal received from a corresponding one of the plurality of datalines to a first node, a driving transistor connected between the firstnode and a second node and through which a driving current correspondingto the data signal flows, a storage capacitor which includes a first endconnected to a power supply and a second end connected to a gateelectrode of the driving transistor, an organic light emitting diodewhich emits light by the driving current, wherein the driving currentflowing through the organic light emitting diode, a light emissioncontrol transistor connected between the second node and an anode of theorganic light emitting diode and which is turned on by an light emissioncontrol signal received from a corresponding one of the plurality oflight emission control lines and which transmits the driving current tothe organic light emitting diode, an initialization transistor turned onby an initialization signal received from a corresponding one of theplurality of initialization lines and which applies an initializationvoltage to the gate electrode of the driving transistor; and a resettransistor turned on by the scan signal and which applies theinitialization voltage directly to the anode of the organic lightemitting diode, wherein the at least one of the plurality of pixelsincludes both an n-type transistor provided with an oxide semiconductorlayer and a p-type transistor provided with a low-temperaturepolycrystalline silicon (LTPS) semiconductor layer.
 10. The organiclight emitting diode display device of claim 9, wherein the switchingtransistor is the n-type transistor provided with the oxidesemiconductor layer, and the driving transistor and the light emissioncontrol transistor are the p-type transistors provided with the LTPSsemiconductor layer.
 11. The organic light emitting diode display deviceof claim 9, further comprising: a compensation transistor whichcompensates a threshold voltage of the driving transistor and isconnected to the driving transistor.
 12. The organic light emittingdiode display device of claim 11, wherein the compensation transistor,the initialization transistor, and the reset transistor are the n-typetransistors provided with the oxide semiconductor layer.
 13. The organiclight emitting diode display device of claim 9, further comprising anoperation control transistor turned on by the light emission controlsignal and which connects the first node and the power supply.
 14. Theorganic light emitting diode display device of claim 13, wherein theoperation control transistor is the p-type transistor provided with theLTPS semiconductor layer.
 15. The organic light emitting diode displaydevice of claim 13, wherein the operation control transistor is then-type transistor provided with the oxide semiconductor layer.